Coated abrasive apparatus



Aug. 16, 1966 D. .J. OLTON COATED ABRASIVE APPARATUS Filed May 6, 1964 INVENTOR Dneck J. OLTON ATTORNEY United States Patent 3,266,197 CUATED ABRASIVE APPARATUS Dirck J. ()iton, Loudonville, N.Y., assignor to Norton Company, Troy, N.Y., a corporation of Massachusetts Filed May 6, 1964, Ser. No. 365,291 3 Claims. (Cl. fill-13?) The present invention relates in general to coated abrasive belt machines and more specifically to such belt machines in which a coated abrasive belt is subjected to forces at an angle to its normal direction of travel which tend to prevent the belt from following its normal and intended path.

Most coated abrasive belt machines have relatively few (forces applied which tend to seriously affect the ability of the belt to follow its normal and intended path of travel. In the usual machine these forces are light enough that conventional tracking equipment can handle them and many variations of tracking devices are available. However, some machines are so used that these forces, which may be termed side forces since they usually tend to force the belt to one side or the other of its normal path, are extreme and beyond the capability of normal tracking devices to correct. These high side forces exist both in connection with abrasive belts used for grinding as in flat platen machines with reciprocating work feeds and also in connection with such belts used as work-feeding belts as in the belt centerless grinder described below.

Centerless belt grinders are designed to grind and/or polish cylindrical workpieces without using chucks or other fixtures to hold the workpiece during grinding. This permits grinding very long tube or round bar stock. Increasing interest in this type of apparatus has led to the development of high horsepower; heavy duty units which will take heavy cuts from normal steel or the like workpieces and which are capable of grinding the newer and harder alloy metals.

In construction, these grinders utilize a coated abrasive belt trained over a driven contact wheel and an idler pulley. The cylindrical workpiece is supported on a steady rest adjacent the contact wheel and travels across such rest between the abrasive belt and a regulating head. This regulating head sometimes is a wheel, but in heavy duty work is usually a coated abrasive belt driven at a slower speed than the actual grinding belt. This regulat ing belt serves to brake the workpiece and to prevent it from reaching the same surface feet per minute speed as the grinding belt. The regulating belt is held under high pressure against the cylindrical workpiece by a platen or back-up plate behind the regulating belt. The regulating belt also serves to feed the workpiece through the ma chine and this is accomplished by setting the regulating belt at an angle from the vertical. This sets up extremely high side forces which act to move the regulating belt off its normal tracking path over the driven and idler pulleys of the regulating head.

The slow speed at which the regulating belt is driven in order to brake the workpiece and to feed it through at the desired rate has prevented the satisfactory use of normal tracking devices such as radiused pulleys, bevelcrowned pulleys, etc. As a result the full capability oi the new heavy duty grinders has not been realized since they were forced to operate at lower grinding pressures where belt tracking was not as much of a problem.

Accordingly, it is an object of the present invention to provide a method and means for overcoming the tendency of coated abrasive belts to improperly track when subjected to high pressures or forces at an angle to the normal path of travel of the belt.

A further object of the invention is the provision of a means to cause a coated abrasive belt to run true even when high side forces are applied to such belt.

3,266,197 Patented August 16, I966 Another object of the invention is the provision of an improved means for use with a regulating belt on a coated abrasive centerless belt grinder.

Additional objects, it not specifically set forth herein, will be readily apparent to one skilled in the art from the following detailed description of the invention:

In the drawings:

FIGURE 1 is a schematic illustration of an abrasive belt centerless grinder utilizing a regulating belt and platen as discussed above.

FIGURE 2 is a schematic View showing the angle of the regulating belt of FIGURE 1 to the vertical and is taken normal to the plane of FIGURE 1..

FIGURE 3 is a perspective view of a platen constructed in accordance with the present invention.

FIGURE 4 is. a. schematic diagram of a flat platen coated abrasive belt machine utilizing a reciprocating feed table.

Generally, the present invention is applicable whereever a problem of tracking a coated abrasive belt due to excessive side forces exists. A particularly acute example of this is in the case of the regulating belt of the centerless grinder described above. More specifically, the invention comprises the provision of a platen or back-up plate for an abrasive belt subject to such side forces wherein a plurality of grooves or relief slots are provided in the face of the platen in contact with the back surface of the belt. These grooves or slots, in all. instances, are parallel to the direction of travel of the belt and under pressure the belt will be forced into these slots and will then satisfactorily resist lateral displacement.

Referring in this connection to the drawings, it will be seen that a centerless belt grinder is schematically illustrated in FIGURE 1 and comprises an endless coated abrasive grinding belt 10 passing over a driven contact wheel 11 and an idler pulley 12. The cylindrical workpiece 13 is supported by a steady rest 14 in contact with the abrasive grinding belt and is held against such grinding belt by the regulating belt 15 which passes between the workpiece l3 and a back-up platen 16. The regulating belt 15 is preferably a cloth-backed coated abrasive 'belt and is trained over a drive pulley 17 and an idler pulley 18. In operation the grinding belt 10 is driven in the direction shown by the arrow on contact wheel 11 and in turn drives the workpiece 13 in the direction shown by the arrow thereon. Regulating belt 15 driven in the direction shown by the arrow on drive pulley 17 travels at a much slower surface feet per minute speed than does the grinding belt 10 and effects a braking action on the workpiece 13. The workpiece 13 will hence travel at the same speed as the regulating belt 15. The path of travel of the regulating belt 15 is at a slight angle A (variable as desired to change in-feed speeds) to the vertical as shown in FIGURE 2 so that as the regulating belt 15 contacts the workpiece 13 it not only slows its rotation to that of the regulating belt 15 but it also feeds the workpiece 13 through the machine in the direction shown by the arrow in FIGURE 2.

The side forces on the regulating belt 15 normally tend to force the belt out of its proper or true tracking relationship to its pulleys l7 and 18. However, as shown in FIGURE 3 the platen 16 is provided with a plurality of slots or grooves 19. The platen 16 is placed across the path of travel of the belt 15 and in contact with the back surface of such belt so that the slots 19 extend in the direction of such travel. As high pressure is applied to the face of the belt 15 the belt is forced against platen 16 and the material of the belt will extend into the grooves 19 providing a resistance to lateral movement of the belt 15.

The particular material of the platen, while usually steel, may be varied as desired. Likewise the number and dimensions of the grooves in the platen may be varied within wide limits depending upon the width of the regulating belt, the pressures to be employed or the like. A typical platen has 23 grooves, 1% inches long and inch deep, with each groove being A inch wide. The lands 20 between the grooves were A" wide. This particular platen has been used to regulate a 6 inch wide, 60" long cloth-backed, grit 50, all resin bonded coated abrasive belt. This specific platen has been run on a model 614B Production Machine Co. centerless grinder at the maximum pressure capable of using a 40 hp. motor driving the grinding belt.

As mentioned above, the problem also exists in other abrasive belt equipment where the grinding belt itself is subject to these excessive side pressures. As schematically shown in FIGURE 4, the coated abrasive belt 21 is driven in the direction shown by the arrow by driving roll 22 and over idler roll 23. The workpiece 24 is held to worktable 25 by a magnetic chuck or the like. (not shown). Worktable 25 reciprocates at right angles to the direction of travel of belt 21 as shown by the arrows. This places a lateral stress or force on belt 21 tending to cause it to deviate from its intended path over rolls 22 and 23. Platen 26 made in accordance with the present invention and disposed behind belt 21 where it presses such belt into the workpiece 24 corrects for this tendency to deviate since the belt will travel with part of its backing riding in the grooves 27 (shown in dotted lines) and hence will resist lateral displacement.

Obviously, many variations and modifications may be made without departing from the spirit and scope of the invention herein disclosed so that only such limitations should be imposed as are set forth in the appended claims.

I claim:

1. In an abrasive belt machine wherein a coated abrasive belt is tracked over at least two rotatable pulleys and in operation is subjected at a point intermediate said pulleys to forces tending to untrack it from its normal path of travel over said pulleys, the improvement comprising a rigid flat-surfaced back-up member behind said abrasive belt and in intimate contact therewith at said point intermediate said pulleys, said back-up member having in the flat surface thereof in contact with said belt a plurality of grooves extending in the direction of travel of said belt.

2. In an abrasive belt machine of the centerless grinder type wherein a coated abrasive regulating belt is trained over at least two rotatable pulleys and engages a rotating cylindrical workpiece at a point intermediate said pulleys to brake the speed of such workpiece and to feed such workpiece through the machine, the improvement which comprises a grooved fiat platen behind said coated abrasive regulating belt at the point of engagement between said belt and said workpiece, said grooves in said platen extending in intimate contact with the back of said belt in the direction of travel of said belt.

3. A method of preventing lateral displacement of a coated abrasive belt traveling over at least two rotatable pulleys and being subject to lateral forces at a point intermediate said pulleys tending to displace said belt from its normal path of travel which comprises: providing a flat surface containing a plurality of narrow parallel relief areas behind said belt at said point intermediate said pulleys; and applying pressure normal to the face of said belt at said point while it travels its normal path to force said back of said belt into said narrow, parallel relief areas, said relief areas extending with their length direction in the direction of normal travel of said belt.

References Cited by the Examiner UNITED STATES PATENTS 1,036,783 8/1912 Bein. 1,421,205 6/ 1922 Fuller 51137 2,477,358 7/1949 Adams 51135 FOREIGN PATENTS 220,503 8/ 1961 Austria.

ROBERT C. RIORDON, Primary Examiner.

L. S. SELMAN, Assistant Examiner. 

1. IN AN ABRASIVE BELT MACHINE WHEREIN A COATED ABRASIVE BELT IS TRACKED OVER AT LEAST TWO ROTATABLE PULLEYS AND IN OPERATION IS SUBJECTED AT A POINT INTERMEDIATE SAID PULLEYS TO FORCES TENDING TO UNTRACK IT FROM ITS NORMAL PATH OF TRAVEL OVER SAID PULLEYS, THE IMPROVEMENT COMPRISING A RIGID FLAT-SURFACED BACK-UP MEMBER BEHIND SAID ABRASIVE BELT AND IN INTIMATE CONTACT THEREWITH AT SAID POINT INTERMEDIATE SAID PULLEYS, SAID BACK-UP MEMBER HAVING IN THE FLAT SURFACE THEREOF IN CONTACT WITH SAID BELT A PLURALITY OF GROOVES EXTENDING IN THE DIRECTION OF TRAVEL OF SAID BELT. 